scsi: remove unused free discard page in sd_done

- sd_done isn't called for pc request so we never call the code.
- we use sd_unprep to free discard page now.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

drivers/scsi/sd.c

@@ -1179,15 +1179,6 @@ static int sd_done(struct scsi_cmnd *SCpnt)
 	int sense_valid = 0;
 	int sense_deferred = 0;
 
-	/*
-	 * If this is a discard request that originated from the kernel
-	 * we need to free our payload here.  Note that we need to check
-	 * the request flag as the normal payload rules apply for
-	 * pass-through UNMAP / WRITE SAME requests.
-	 */
-	if (SCpnt->request->cmd_flags & REQ_DISCARD)
-		__free_page(bio_page(SCpnt->request->bio));
-
 	if (result) {
 		sense_valid = scsi_command_normalize_sense(SCpnt, &sshdr);
 		if (sense_valid)